Very faint hissing sound

[Habbibie]

I swear every week theres something wrong with my expedition... its cursed I tell ya!

Anyways yesterday I noticed there a very faint hissing happening, alot like the noise you get in your ear when you stand by a concert speaker too long that when you leave that hissing in your ear stays... identical to that noise.

It's in the interior, I cant hear it outside and I dont even know where too look for it its heard by both ears, I thought initially it was either the stereo speakers or the air vents but turning those off doesnt eliminate the noise, also I noticed when I turn off the truck the hissing continuous for about 5 seconds then slowly disappears, again I cant pin point a location where its coming from but I had two passengers in the truck yesterday and they both heard it too.

Anyone run into this issue before?

 

[stamp11127]

Clamp the hose on the vacuum booster and see if you still hear it.

 

[Habbibie]

Clamp the hose on the vacuum booster and see if you still hear it.

Ok when I get home I'll do that and give back an update.

 

[BRIANGEE]

I swear every week theres something wrong with my expedition... its cursed I tell ya!

Sheesh! Tell me about it! This will be my last ford. I just want to TRY to get my money's worth out of it since I've only owned it a year.

Do your AC controls work okay? Front and back?

 

[Habbibie]

Do your AC controls work okay? Front and back?

Yes

 

[Trainmaster]

Being it continues for a few seconds after turning off the car, it's probably a vacuum or pressure leak. Check your fuel lines - a leak will be obvious. Vacuum leaks are another story; they're hard to find. But they get worse, then you find them.

 

[stamp11127]

Hear a leaking fuel line inside the cabin? OP didn't mention anything about smelling fuel.

 

[ChrisOIFdoc]

Rear compressor heater core etc.? Maybe?

 

[Habbibie]

Ok so I just got home, I started the truck up.... no hissing, idled it for about 15 minutes.... still no hissing, so I then drove it around the block, still couldn't hear the hiss, so I pulled back on to the driveway, put it back in park and shut off the engine, only then I realized the hiss was there when I shut the motor off that I can clearly now hear it slowly pronouncing away. I started the engine up again, went and crimped the vacuum hose (with a locking needle nose pliars) while it running and ran back inside the interior but I couldn't hear the hiss over the engine stuttering grasping for air.

Like I said it's a very faint hiss... if you dont concentrate on it you wont know it's there

 

[BRIANGEE]

So the question becomes do you really want to go looking for trouble? If it's so small you have to concentrate to hear it and it's not causing any kind of trouble I'd just leave it be until it gets worse. It's probably just an AC vacuum control line or something bleeding off because of a small pinhole or failing connection.

I suppose you could rule out the AC controls (assuming your year is vacuum controlled) by disconnecting the vacuum hose that goes through the firewall behind the battery, cap the end you disconnected from, then run your vehicle, let it build vacuum for a few seconds, then shutoff and see if you can still hear it. If you can't then you know it's some AC lines - if it still hisses then something else.

 

[Habbibie]

I narrowed down the cause of the noise, brake booster... after releasing the brake pedal the hissing comes on

Edit: well since now I know, that's a relief, down side is I gotta go to Minnesota for a project for the next two weeks so sadly I'll have to wait until I get home from the trip to get dirty

 

[1955moose]

I was gonna say someone threw a snake in your car! He was grasping for air! It gets hot in your SUV this time of year! Sorry I'm bored, and earlier posts I just can't help myself! Leaking booster/check valve/booster hose. Henry does this have anything to do with the brake Abs problem you had about 3-4 weeks back? Did you ever fix that problem, this is the same 7 mpg vehicle?

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[Habbibie]

I dont know if the abs pump issue is related yet but I replaced the pump a while ago and it's been working fine since, and to be honest Steve I dont even know the mpg of my expy anymore lol, it's been on the same tank for the past 4 months... it gets driven 4.2 miles round trip every Sunday & only on Sunday's.

 

[Habbibie]

I dont know if the abs pump issue is related yet but I replaced the pump awhile ago and it's been working fine since, and to be honest Steve I dont even know the mpg of my expy anymore lol, it's been on the same gas tank for the past 4 months... it gets driven 4.2 miles round trip every Sunday & that's the only driving it does now

 

[SEPTIC PROFESSOR]

Dude, it's time to junk it dude.

 

[1955moose]

Nah, Habbibie can't junk it! It's personal now. All the work he's done to it. Besides he's got a company vehicle for a daily driver. If he gets rid of it, he might go away, can't have that! We go way back.

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[JExpedition07]

Trucks too nice to junk, he just did rockers and radiator supports and put in a replacement motor.....junk it?!?! Has somebody lost their mind?

 

[1955moose]

We've got people on the forum driving rolling heaps ready for the boneyard that want to keep there's. His is great in comparison!

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[Habbibie]

Haha sad but true, I'm in the crappy position of being allowed to say "I've invested more into it than it's worth"

Couple things that come to mind as you guys mention it, its the only project I gave left in my life, I sold my old(er) house and pocketed the extra profit but in turn bought a much newer house and it doesnt have s soul so to say
.. it's still too new for anything to be worked on so boredom for me is in full effect, truly only reason I'm even still keeping it is for a "what if" something happens to my wife's minivan, I have a (relaiable) back up 7 seater for her right away free of charge other wise I'd leave the expy and return to either an f150 or f250... they're better suited for drivers 6ft+ tall, and Finally like @JExpedition07 & @1955moose said I got too much invested in it it's stupid to sell it now for a huge loss

Anyways what am suppose to do svkht this hiss? Does that carb cleaner on vacuum leak trick still work on these trucks?

 

[BRIANGEE]

Habibbie, yeah the carb cleaner trick works but I've never had much luck with it personally. I have better luck w/ a graphing scan tool set to short term fuel trims and watching it as I spray propane around. Sometime the idle change is too small for me to tell w/ these monstrous V8's so seeing the change on a graph is a big help.

What reliable minivan do you have? I've been trying to find a Toyota Sienna for a couple of months now. I just trashed our family vehicle, an Odyssey, because I thought it had a timing chain and NOPE - it had a belt - it was THE original belt and it went 260K miles without being changed. Being an interference engine (aren't they all?) it trashed the valves. I could kick myself.